The present invention generally relates to an electrical switch and more particularly, to a high precision electrical switch of a small size.
Conventionally, for electrical switches with contacts employed, for example, for detecting positions of various objects, there have been employed switches which adopt a reversing mechanism and those which utilizes a leaf contact, for example. However, each of such known switches, which employs a plate spring, has such a disadvantage that scattering of functioning positions of the contacts thereof tends to be large.
In order to eliminate the inconvenience as described above, there has also been conventionally proposed an electrical switch which is so arranged that an electrically conductive spherical member urged by a return spring contacts a pair of fixed contacts for constituting normally closed contacts, while the spherical member is adapted to be spaced from the respective fixed contacts against the urging force of the return spring by depressing a plunger.
The known switch arrangement as described above, however, still has such drawbacks that not only cost of the switch becomes high due to employment of the spherical member, but also the switch itself tends to be large in size, since the plunger, spherical member (movable contact), and return spring are aligned, as it were, in series. Meanwhile, the sliding span or distance of the plunger should preferably be as long as possible for stable operation, with a less adverse effect to accuracy due to a looseness or side play, but in the switch arrangement referred to above, if the sliding span is set to be long, the size of the switch itself is inevitably increased, and thus, a sufficiently long span can not be provided for achieving a high accuracy.